The preceding chapters of this book that deal with animals are restricted to mammals and birds, with only one chapter on beetles and brief mentions of the Argentine ant (Iridomyrmex humilis) and Drosophila suboscura in Chile. Despite the rich collection of facts and the interpretations given by the authors of the preceding chapters, any attempt at predictive generalisation is very difficult. The same conclusion holds after reviewing the many chapters on animal invasions that have been produced during the overall SCOPE project on biological invasions (see, for instance, Brooke et al., 1986; Bruton & van As, 1986; Ehrlich, 1986; Macdonald et al., 1986; Mooneye et al., 1986; Moran et al., 1986; Moyle, 1986; Myers, 1986; Pimentel, 1986; Simberloff, 1986; Zimmermann et al., 1986; Lawton & Brown, 1987; Ross & Tittensor, 1987; Brown, 1989; Usher, 1989). Almost exclusively, the invasion of oceanic islands seems to follow consistent patterns (see Cooper & Brooke, 1986; Moulton & Pimm, 1986; Coope, 1987; Holdgate, 1987; Loope & Mueller-Dombois, 1989), a result that could be predicted and in accordance with Williamson (1981). But for larger land masses, it is difficult to discern patterns as clearly as for islands. In his concluding remarks on vertebrate invasions, Ehrlich (1989) draws attention to our inability to make some kinds of predictions, but optimistically (and pragmatically) he contends that ‘considering the enormous complexity of the problem, what can already be predicted is far from trivial’ (p. 326).